I am considering an M&P AR 15 - but I am not sure I want a gun that doesn't have a chrome lined barrel and chamber - just wondering how durable the M&P's are for sustained shooting and wear of the finish

Chrome lined barrels are very good, but aren't the be all end all that many believe they are. Some of the new Melonite treated barrels are as accurate and durable, maybe more so, as the Chrome lined barrels. I wouldn't let Chrome lining be a deal breaker.

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SFC, US Army, Retired

Which M&P are you considering? Most M&P 15s have a chrome lined barrel. The ones that are not chrome lined are treated with Melonite, which is showing to be a very good alternative, with some saying that it is superior to chrome lining.

I am not aware of a S&W barrel that isn't either chrome lined or Melonite treated... although S&W no longer calls it Melonite due to trademarks, it is now corrosion resistant finish, or something along those lines.

It reminds me of the weapon I carried for years in the USAF and in Panama in 1989.

We had to keep them pretty clean and lubed in the hot and humid environment and although not as hot and humid as Panama here in TX there is enough to make it a nice thing to have

That model has a chrome lined barrel.

If unsure, just read the paper label wrapped around the handguard for full details on the barrel.

If you shoot a lot of corrosive ammo you'll like chrome lined barrels.

Melonite vs Chrome barrels


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Advantage of chrome lining = hardness, heat, wear resistance.

Con of chrome lining = increased production cost, more complex production process, the bore is cut to accommodate the thickness of the chrome lining. This can potentially decrease the accuracy of the barrel.

Non chrome lined barrel = Increased potential for accuracy because there's no accommodations made the additional chrome lining. Unlined barrels can be 4140, 4150, Stainless, or chrome moly vanadium.

Melonite treated barrel = Most people mistakenly think this is an applied finish. It is a hot salt bath nitriding process that alters the crystalline structure of the barrel steel to a depth greater than chrome lining. You get the best of both worlds with a Melonite treated barrel: similar properties to hard chrome without the potential for decreased accuracy.

Now what does that mean to the average civilian firearms enthusiast for whom getting to a 10,000 round count takes a few years? Not much. I have all three types of barrels: chrome lined, melonite, and unlined CMV. You'd think I'd be able to give evidence of a practical difference between all three types, but I can't. I don't shoot to the bleeding edge of 5.56 range, nor do I have I attained the level of marksmanship skill to eke out the small difference.

What is the ownership difference? I pull a flexible rod with a CLP moistened patch down the barrel of my unlined CMV barrel at minimum once every two months to prevent corrosion. To tell you the truth that CMV barrel on my budget AR probably has more erosion from being fired than anything else. The chrome lined and Melonite barrels are more corrosion resistant and less worrisome. I still pull a CLP moistened patch down their barrels every two months.

Good luck from the former forum AR-15 guinea-pig tester,

John

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-John

I see what you did there.

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-John

Should that be done in the shop or at home? Now we're just being mean.

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SFC, US Army, Retired

Don't be feeding the bear now gentlemen!

Posted by a moderator even

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~ From the Land of Lobstah ~

If left unattended for long enough after shooting corrosive a chrome lined barrel will still be a mess...it'll just have less permanent damage than a non chrome lined. Don't ask me how I know.

It all depends on who makes the barrel, not necessarily what the surface treatment or type of rifling is used. A quality barrel is a quality barrel.

Match and target barrels sacrifice some durability for accuracy. Hard use barrels are often double chrome plated and use steels that withstand extreme temperatures better at the expense of absolute accuracy, and most commercial barrels fall somewhere in between.

For those not shooting competitively or firing registered machine guns or dedicated bump fire guns it's all of little consequence.

My play gun is the only one with a chrome lined barrel. The others have match barrels. It's doubtful I'll wear any of them out.

People obsess over the most random of specs when it comes to these rifles, but if it runs well and shoots well why mess with it internally?

My moe mid 4150 CMV 5r 1/8 barrel has held up exceptionally well. Close to 7000rd(mostly tula) and it still shoots 2-3moa with most decent ammo. I've been extremely hard on this rifle and have yet to experience a malfunction or see a decrease in accuracy.
I also own three other m&p rifles with melonited barrels and all have held up extremely well. I don't know if it makes much difference, but I only use hoppe's 9 cleaner and oil on all my guns. Based on my experience with the m&p rifles and pistols, S&Ws melonite finish is definitely good to go.

My question for you is this -

"How many non chrome lined / non AR style weapons do you have?"

Do you have any problems with them?

What corrosive ammo are you planning on running?

Yes. Chrome just adds an extra layer of protection against corrosion. It doesn't actually stop it.

Are modern handgun barrels chrome lined? I have no idea. It never occurred to me to even find out. I would say they are probably my only none chrome lined barrels. I'm also not sure about my Colt 6721. Otherwise everything else I have is AKs and they are ALL chrome lined. I shoot plenty of corrosive 5.45 and 7.62x39.

OK, virtually no handgun barrels are chrome lined. They don't need the increased resistance to heat and abrasive wear because they don't generate the bore/chamber temperatures & pressures that require it.

When doing the CQB portion of our training, our dedicated training rifles will fire in the neighborhood of 2000 rounds per week. Without a chrome lined barrel, bullets start going through the target sideways in a couple of months. We used to have a barrel of shot out barrels.

Now, if you're not firing strings of multiple shots in very short times, the lack of chrome lining may not be as apparent. It's the heat build up in the barrel, abrasive wear from the bullets and flame temperature from the powder that accelerates the wear.

*cough* current production Brunitron finish Beretta 90-series pistols *cough*

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-John

Kindly note the qualifier "virtually".

I bet if you make a list of all weapons that are chrome lined you will be amazed at really just how few there are (Non AR15 and AK pattern weapons). Its really just a leftover from the good ol days.

Shoot modern ammo and/or clean your weapon. Problem solved.

From what I've read I would rather have the melonite treated barrel above all else. Nothing wrong with chrome lined either. So melonite would be my choice due to lower cost factor.

From what I've read many times, chrome cannot be applied in the barrel evenly which generally results in decreased accuracy. I'd take Melonite (or whatever it really is these days in the M&P line) over chrome any day. The AK boys still shooting corrosive primed ammo might like chrome a whole lot better. Good luck!

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Webfarmer

There's a misconception that the hard chrome lining of gun barrels is like bumper chrome.

Bumper chrome is/was thick and soft and had to applied over a copper under layer. Anyone who had a nickle plated .357 and fired a lot of hot loads saw the plating disappear from the front of the cylinder.

By contrast, hard chrome (and it's various patented variations) generally runs 72-72 on the Rockwell C scale. It achieves a bond with the parent material on the molecular level without underlayment. It's also less than 0.001 inches thick, frequently 0.0002 inches. That's much less than the allowable variation of bore/groove diameter in the average gun barrel. There would be little or no need to produce oversize dimension barrels with that type of plating

I can't speak to the difficulty of achieving an even plate in a barrel bore. I do know that platers go to extreme effort to do so. The definition of "even" also makes great difference. Exactly how many significant zero digits are there after the decimal point?

FN, amoung others, is producing precision rifles with plated bores. Judging by the groups achieved by many folks in T&E of the rifles, if there's a negative effect, mere mortals can't detect it.

This isn't to say that all plated bores are created equal. I noted an AR builders ads for "extra thick plated bores" in some of their barrels. "For high volume shooters" I have to assume those were either a mistake or someone was trying to build oversize bores/grooves to acceptable dimensions.